Merge pull request dateutil#413 from pganssle/prepare-2.6.1

Prepare 2.6.1

Release 2.6.0.

Merge pull request dateutil#255 from pganssle/prepare-2.5.3-release

Prepare 2.5.3 release.

Merge pull request dateutil#231 from pganssle/prepare-2.5.2

Prepare 2.5.2 release.

Merge pull request dateutil#223 from dateutil/prepare-2.5.1-release

Prepare 2.5.1 release.

Merge pull request dateutil#192 from dateutil/prepare-2.5.0-release

Prepare 2.5.0 release

Prepare 2.4.2 release.

2.4.1 release

release version 2.4.0

2.3 release